Communication devices such as terminals are also known as e.g. User Equipments (UE), mobile terminals, wireless terminals and/or Mobile Stations (MS). Terminals are enabled to communicate wirelessly in a cellular communications network or wireless communication system, sometimes also referred to as a cellular radio system or cellular networks. The communication may be performed e.g. between two terminals, between a terminal and a regular telephone and/or between a terminal and a server via a Radio Access Network (RAN) and possibly one or more core networks, comprised within the cellular communications network.
Terminals may further be referred to as mobile telephones, cellular telephones, laptops, or surf plates with wireless capability, just to mention some further examples. The terminals in the present context may be, for example, portable, pocket-storable, hand-held, computer-comprised, or vehicle-mounted mobile devices, enabled to communicate voice and/or data, via the RAN, with another entity, such as another terminal or a server.
The cellular communications network covers a geographical area which is divided into cell areas, wherein each cell area being served by an access node such as a base station, e.g. a Radio Base Station (RBS), which sometimes may be referred to as e.g. “eNB”, “eNodeB”, “NodeB”, “B node”, or BTS (Base Transceiver Station), depending on the technology and terminology used. The base stations may be of different classes such as e.g. macro eNodeB, home eNodeB or pico base station, based on transmission power and thereby also cell size. A cell is the geographical area where radio coverage is provided by the base station at a base station site. One base station, situated on the base station site, may serve one or several cells. Further, each base station may support one or several communication technologies. The base stations communicate over the air interface operating on radio frequencies with the terminals within range of the base stations. In the context of this disclosure, the expression Downlink (DL) is used for the transmission path from the base station to the mobile station. The expression Uplink (UL) is used for the transmission path in the opposite direction i.e. from the mobile station to the base station.
In 3rd Generation Partnership Project (3GPP) Long Term Evolution (LTE), base stations, which may be referred to as eNodeBs or even eNBs, may be directly connected to one or more core networks.
3GPP LTE radio access standard has been written in order to support high bitrates and low latency both for uplink and downlink traffic. All data transmission is in LTE controlled by the radio base station.
Within telecommunication systems, such as within a Global System for mobile communications (GSM) Enhanced Data Rates for GSM Evolution (EDGE or EGPRS) Radio Access Network (GERAN) network, so called Packet Switched (PS) Temporary Block Flow (TBF) may be assigned to a device and used to enable transfer of user data between e.g. a Radio Base Station (RBS) and a Mobile Station (MS), such as a wireless device. In a GERAN network, a PS TBF may be assigned a Temporary Flow Identity (TFI) value.
The TFI itself is a 5-bit field encoded as a binary number in the range 0 to 31, which may be typically provided to the MS by the GERAN network upon TBF assignment. The TFI value may uniquely identify a TBF among concurrent TBFs in the same direction, UL or DL, assigned the same Packet Data Channel (PDCH) resources on the same carrier. The same TFI value may be used concurrently for other TBFs on other PDCH resources in the same direction and for TBFs in the opposite direction, hence a TFI is a unique identifier on a given PDCH resource.
A Radio Link Control Medium Access Control (RLC/MAC) block sent on a given UL/DL carrier may be associated with a certain TBF and may thus be uniquely identified by the TFI together with, in case of an RLC data block, the direction, UL or DL, in which the RLC data block is sent; and in case of a RLC/MAC control block, the direction in which the RLC/MAC control block is sent. In case Starting sequence number (SSN)-based Fast Acknowledge/Non-acknowledge (Ack/Nack) Reporting (FANR) is used, the TFI identifying the TBF being acknowledged may be included in the Piggy-backed Ack/Nack (PAN) field.
This means that, e.g., every time an MS receives a DL data block or control block on a given carrier, it may use the included TFI field to determine if the block belongs to any, there can be more than one, of the TBFs associated with that very MS. If so, the block is intended for this MS, whereupon, the corresponding payload may be decoded and delivered to upper layers, but otherwise discarded. In the UL direction, the behavior may be the same, i.e. the network may use the TFI value to identify blocks that belong to the same TBF and therefore belong to the MS assigned the use of that TBF. This is an existing mechanism that may be used in GERAN networks for facilitating the multiplexing of multiple users on the same PDCH resources on a given carrier.
The need for TFI uniqueness within the context of any given set of PDCH resources, on a given carrier, assigned to multiple MS limits the number of concurrent TBFs and thus devices that may share the same radio resources on that carrier. In case of devices supporting Downlink Multi-carrier (DLMC) mode of operation, see 3GPP TS 44.060, 3GPP; GERAN; Mobile Station (MS)—Base Station System (BSS) interface—Radio Link Control Medium Access Control (RLC/MAC) protocol, the limitation may be even more severe as each DL TBF supported using DLMC may be assigned the use of PDCH resources on multiple DL carriers. In other words, assigning a TFI that is to be unique across a set of multiple DL carriers may limit the number of devices that can share PDCH resources associated with that set of DL carriers to a greater extent compared to the case where an assigned TFI only needs to be unique within the context of each DL carrier within the same set of DL carriers. As a result of this, it was decided that the TFI addressing space used before the introduction of the DLMC feature in 3GPP GERAN Rel-12 was insufficient for supporting the DLMC feature, assuming the current and projected increase of PS traffic observed in GERAN networks over the world. See GP-130662 DLMC—Extended TFI Addressing Space, 3GPP GERAN#59, Ericsson & ST-Ericsson.
In the context of mobile stations (MS) operating in a DLMC configuration, see GP-121158 WID: Downlink Multi Carrier GERAN, 3GPP GERAN#55, Ericsson & ST-Ericsson, a TFI expansion, referred to as extended TFI (eTFI), may be needed to increase the TFI addressing space, when such MS are multiplexed on the same radio resources of a given set of DL carriers. Different approaches for TFI expansion exist for radio blocks carrying user plane payload wherein a Cyclic Redundancy Check (CRC) code may be used solely for radio block error detection, see WO2013070163A1, Methods and devices for providing TFI, Liberg, Sundberg, Schliwa-Bertling and Eriksson. A radio block is understood herein to comprise a radio block header and a payload information field, e.g., control plane payload or user plane payload, supplemented with a number of parity bits used for verifying the validity of the radio block header and payload. In addition, there is an approach that may ensure control plane payload, i.e., Packet Associated Control Channel (PACCH) blocks sent to a MS in a DLMC configuration with an eTFI assignment may not be correctly received by a non-eTFI capable MS and vice versa, see GP-131135—Extended TFI Addressing space for DLMC, 3GPP GERAN#60, Telefon AB LM Ericsson. PACCH blocks are an example of radio blocks. See also GP-130662 DLMC—Extended TFI Addressing Space, 3GPP GERAN#59, Ericsson & ST-Ericsson.
In GERAN, a number of logical channels such as the Packet Associated Control Channel (PACCH) and Slow Associated Control Channel (SACCH), to mention a few, are based on the channel encoding where a shortened FIRE code is used, appending a 40 bit parity bit field to 184 information bits, see 3GPP TS 45.003 v12.0.0, 3GPP; GERAN; Channel Coding.
These 40 parity bits can either be used to correct or detect errors or both detect and correct errors.
FIRE-encoding is one of multiple available radio block encoding techniques, which map a field of information bits to a code word, where the Hamming distance between possible code words facilitates correction and/or detection of errors when decoding the radio blocks.
The approach presented in GP-131135—Extended TFI Addressing space for DLMC, 3GPP GERAN#60, Telefon AB LM Ericsson may provide the desired extension of the TFI space when sending a FIRE-encoded control block, e.g., a PACCH block, to a MS in a DLMC configuration with an assigned eTFI. This may be done using a DL radio resource also being monitored by a non-eTFI capable MS, i.e., a MS not supporting DLMC, or a MS in a DLMC configuration without an assigned eTFI, for the potential arrival of PACCH blocks. That is, the solution in GP-131135—Extended TFI Addressing space for DLMC, 3GPP GERAN#60, Telefon AB LM Ericsson may prevent the non-eTFI capable MS from declaring a PACCH block sent to a MS in DLMC configuration with an assigned eTFI to be valid. The approach described in GP-131135—Extended TFI Addressing space for DLMC, 3GPP GERAN#60, Telefon AB LM Ericsson may also prevent an eTFI capable MS in a DLMC configuration with an assigned eTFI from declaring a PACCH block sent to a non-eTFI capable MS to be valid.
This is because the FIRE code is a class of cyclic block codes used both for burst error correction and error detection. The burst error correction capability of the FIRE code is defined by the length b of the shortest uncorrectable burst error, see Digital Communications (5th edition), Proakis & Salehi, McGraw-Hill International edition.
An existing approach for extending the TFI space for PACCH blocks is captured in GP-131125—Extended TFI Addressing space for DLMC, 3GPP GERAN#60, Telefon AB LM Ericsson, and implemented in 3GPP TS 45.003 v12.0.0, 3GPP; GERAN; Channel Coding and constitutes the XORing of the three bit eTFI value and a three bit fixed pattern, i.e. all 1's, with a subset of the PACCH block parity bits. The fixed pattern of three bits is used to ensure that even eTFI values with low Hamming weight may ensure good false detection performance for legacy MSs decoding the PACCH block that assumes no XORing of bits has been done at the transmitter side. The Hamming weight may be effectively determined by comparing the set of bits comprising the eTFI value assigned to one device to the set of bits comprising the eTFI value assigned to a different device on a per bit position basis, whereby the greater the differences of the assigned eTFI values when considered on a per bit position basis the greater the Hamming weight (Hamming distance). Legacy devices may be considered as having been assigned an eTFI value of all zeros for the purpose of determining the Hamming weight. The “Hamming weight” for a sequence or string, for example, may be the number of symbols that differs from “0”. In a typical binary case the “Hamming weight” may be the number of “1's” in the sequence. The method does however not provide the TFI uniqueness, and false detection performance, that may be required when multiplexing eTFI capable DLMC mobiles on a PDCH. To exemplify the problem, FIG. 1 depicts the 40 parity bits generated by the FIRE encoder and a scenario where the methodology described in GP-131125 is used under the assumption that two eTFI capable DLMC devices A and B are multiplexed on a the same PDCH. Device A is assigned eTFI=‘000’ and device B is assigned eTFI=‘001’. This Figure shows a BTS transmitter send a PACCH block to device A with an assigned eTFI=000. Then, device B with assigned eTFI=001 will perform XORing of the bits in bit positions 0, 19 and 38 with the 1st, 2nd and 3rd bits respectively of the three bit fixed pattern, i.e. all 1's, and the bits in bit positions 1, 20 and 39 with the 1st, 2nd and 3rd bits respectively of its assigned eTFI=001, i.e., it assumes eTFI=001 has been XORed into the transmitted PACCH block, and thereby introduces a single error in bit position 39 of the recovered PACCH block. However, due to the error correction capability associated with the FIRE code, device B will correct this induced error and consider the PACCH block to be valid, and therefore, further consider the TFI field in the header of the PACCH block. If the TFI value in the header matches its assigned TFI value, device B will attempt to act on the information carried in the PACCH block even though it was sent with device A as the intended recipient. This may then lead to unpredictable operation within device B which includes the potential for aborting its corresponding DL TBF, thereby resulting in the failure to deliver the intended user plane payload.
As outlined above, the DLMC feature may require an expansion of the TFI field. However, existing methods for TFI expansion may result in one or more unintended recipients concluding they have received a valid TBF block and other errors leading to an unwanted and unpredictable behavior in DL as well as UL.